Signal distortion indicating device



Patented Aug. 1, 1933i lliure-o 'STATES 1 .rri=:N"rA orricsI Thisinvention relates toelectrical measuringY systems and particularly tomeans for deter-V mining the existence and magnitude oi distortion oftelegraph signaling impulses produced in 5 the course of transmittingthe impulses.

In the transmitted` telegraph signals, each made up of a pluralityoflimpulses and each impulse having a definite length, distortion of theimpulse and therefore of the signal, may be produced by various,causes-.inherent inthe line or in the apparatus connectedtherewith orboth. The distortion with whichthis invention is concerned manifestsitself inlengthening 01 shortening the impulsesy .which constitute thesignals transmitted over the line. This lengthening or shortening of theimpulses interferes with ,the proper recordation of the signals at anystation connected to the. line and, consequently, impairs the efliciencyof transmission.

Frequently, printers have been employed for monitoring purposes intelegraph ofces. These printers were employed for communicating withsubscribers and repeater stations, measuring orientation margins eitherin connection With `routine tests of kWorking circuits and when locatingreported trouble. There has also been devised a distortion measuringrdevice' wherein there is eliminated the.y necessity oi a `printer formonitoring purposes. Such a ydevice is'disclosed in Patent No.1,871,916, granted Aug. 16,

1932, to R. E. Pierce, Serial No. 478,745, led August 29, 1939, whereintwo line relays and the receiving part of a start-stop distributor areused in combination with a loud speaker are rangement which aiords `anaudible indication whenever the orientation setting of the distributorring is such that the armatures oi `the line relays reverse theirpositions While the distributor brush is on any one of. the` iiveselectingsegments of the distributor. 'Ihe selecting segments are thoseAcorresponding to the segments that would be connected to the selectingmagnetsk of a printer if one were to be used. The *opera-1v tion of theloud speaker` is used in obtaining' orientation limits in the usual Wayso that sub.- stantially the same results may be secured as if theattendant were measuring the orientationV margin while observing theprinted copy or tape with the printer set. It has also been the prac-vtice in telegraph systems to provide circuits fordeterminingtheexistence and magnitude of distortion wherein a distortion indicatinginstru--V ment is made to respond to a special predetermined combinationof impulses, which arrangecoming lines circuits, K412, 12', 12,.repeater or areceivingy station in` atelegraph ment makes it necessaryto disconnect al line circuit from service in order to test it.

An object of this invention is to determine in la simple, emcient andeconomical manner the existence and i magnitude of lengthening or 60shortening or" signals incoming at a repeater or a receiving station.

This object, morespecificallystatedis to indicate by meansfof' ameasuring device, such as a milliammeter, the magnitude of thedistortion without'resorting to orientationof a distributor ring toobtain this information.

Another object is to utilize the incoming message signal impulsesthemselves for operating the distortionindicating instrument whereby thecircuit being tested may bemaintained in continuous use for transmittingmessages While it .is being tested.

. According to the present invention the 'pres-l ence and magnitude ofthe distortion is determineddirectly" by amilliammeter without the useof monitoring printers `andvifitl'iout resorting to the orientation ofthe monitor distributor ring. With this` invention an arrangement isprovided whereby the total. distortion on a working printer circuitwithin certain predeterminedk limits may be readV directly yon' a meterWithout any manual manipulation of the monitoring distributor. v i

The system whereby this result is accomplished comprises, inoneembodiment, a plurality o indicating circuits and la speciallyconstructed distributor connected thereto whereby one of said circuitscorresponding to the magnitude of the distortion present is selected andcaused to give an indication according to the magnitude of thedistortion of the. impulsesarising at the particularinstantof timeyunder consideration.

Other objects andfeatureswill appear in the following detailedspecification and appended claims when taken in conjunction with theaccompanying drawing of which;y

Figure 1. illustrates an embodiment of the in ventionwherein theymonitoring distributoriis provided with threes'egmented rings; and

Fig. 2v shows a modication of the distributor of Fig. 1 wherein thedistributor comprises only two segmented rings.

(Like, parts are designated by like reference characters. i

Referring to Fig. 1 loop circuitsv 11, 11', 11", etc. are respectively4connected in series with inetc.; at `a system designed to transmitsignalcombinations,

circuit l1 includes a spring jack 13 located in the face of a test boardrepresented diagrammatically by block 14.V Other spring jacks 13', 13",etc. provided in the :face of test board 14 for line circuits l12', 12,etc., which Vmay extend to a 4plurality ci distant stations. The loop`circuits are connected to the line circuits in parallel with thereceiving equipment R shown diagrammatically by blocks 15, 15', 15",etc., whereby the line signals may be received at the test board. Thetest board 14 is` equipped with a plug 16 which is connected to theinput side of a test circuity shown abovethe test board in Athe drawingand which is adapted for insertion `in any one of the loop circuit jacks13.132313", etc. a meter circuit plug 18 adapted for insertion in a testjack 19 which is connectedto the' output side of the test circuitwhereby the magnitude of distortion in the vincoming signal is in-`dicated by the deection of the needle on the meter.

The loop circuit which is assumed hereinto assumed herein to be normallyclosed and normally energized. The lower windings are connected in avcontinuously closed circuit comprising a biasing battery 23 and aregulating resistance 24. The Aline current normally flowing through theupper windings of the relaysflows in a direction opposite to thatflowing through the lower windings Vand is of such strength as topredominate over the latter. The biasing current ilowing 'through thelower windings is regulated by resistance .24 and is therelfore made tobe of suiiicient strength to operate the relays every time the lineopened.

The operation of relay 22 in response to a or loop circuit is `7 nocurrent or open impulse from a distant station causes the armature ofrelay 22y to engage its left-hand contact and thereby to close a circuitextending from the positive pole of groundedv battery 25 armature andleft-hand contact of relay`22, through the winding of release magnet 26,conductor 2'7, contact 28 closed byv the insertion ofplug 13 into jack19, strap 29 to ground. Magnet 2S operates and thereby releases brush 30which starts torotate in the directionY indicated' by theV arrow overthe distributor D. 7-

The distributor D is of the start-stopI `type used in receivingapparatus offstart-stop printing telegraph systems.` Brush 30 which isnormally restrained from moving by the latch under the control'A ofrelease magnet 26, is driven by a constant speed motor through afriction clutch, neither of which is shown'but whichare Well understoodin the art. The distributor comprises three concentric segmented rings31, 32 and 33,

which are shownhere as developedfor the purpose of illustration. rTheinner ring 31 Ais constituted of one long and lone short segment, the

short segmentwhich is engaged by brush 30 in` its normal position beingleft dead andthe 1t is also equipped with a meter17 and,

of current and no current impulses. Loop long segment being connected tothe positive pole of grounded battery 34. The outer ring 33comprisesilve short segments A1 to A5 of equal length corresponding tothe signal impulses of a five-unit code, six long segments Bi to Bc oi'equal length and one dead segment which brush 30 engages when it is inits normal position. The length `of segments A1 to As is determined bythe amount of reiinement required in indicating the distortion of thesignals. inthe illustration described herein the segments fn to A5 aremade one-quarter the length of a unit length or dot impulse andtherefore allow a maximum permissible distortion of one-half a segmentlength which is one-eighth of a unit length or dot impulse, or 121/2%distortion. Segments A1 tons are connected in multiple to conductor 35.The segments B1 to Bs are shown herein as each fhaving a length threetimes that of one of segments A1 to A5 and are capable of indicating'distortion of 121/2% to 25%. Segments B1 to Bs are connected inmultiple tov conductor 36. The middle ring 32 comprises eleven segmentseach having a length twice that of one of segments Ai to As and onelongsegment with which brush 30 is in engagementwhen it is in its normalposition. V'1`he.alternat`c segments C1 to Cs of ring 32 are connectedin multiple to conductor 37,

` the remaining segments being left dead.v Segments C1 to C6 provide forindicating distortion exceeding 25%.

Incomingsignalsare ordinarily considered satisfactory when thedistortion present therein is within the limits of Zero' and 121/2%. Ifperfect signal impulses are received, brush 30 will be passing over thecenter line of a segment A1 etc., of ring 33 at the time the impulse isreceived. If the brush is passing over either the ijront or rear edge of-a segment A at this moment, the distortion present will be 12X/2%. Iithe brush is between the front edge of a'segment B oi ring 33 and thefront edge oi an adjacent segment C1, C2 etc. of ring 32, the distortionwill be between 1212% and 25%. If the brush is on a segment Ci, Cr etc.the distortion will be in excess of 25%.

The conductors 35, 36 and 37 are respectively connected to the windingsof relays 38, 39 and 40 whereby one or more of theserrelays will operatedepending on the position of brush 30 at the time the armature of relay22 moves from one of its vcontacts to the other in response to anincoming signal impulse. lt is while the armature is passing betweencontacts that the positive pole of grounded battery 34 is connectedthrough the distributor D to the winding of` one or more of relays 33,39 and 40., Relays 38, 39 and`40 `which are oi the biased type, areselectively operated by means of `brush 30 to cause a negativepotentialfrom one of the batteries 41,

'42 and l43, that is, the one associated-with the selected relay, to beimpressed on the grid of the associated vacuum tube of tubes 44, and 46.The normal space current of the selected vacuum tube which normallymaintains its associated relay of relays 47, 48 and 49 operated, isblocked bythe negative potential on the grid to thereby deenergize therelay associated with the selected vacuum tube circuit. Relays 47, 48and 49 are also of thebiased type and therefore the deenergized relayallows its armature to fall back into engagement with its back contactwhereby a circuit is closed from grounded battery 50, through thearmature Vand back contact of, the deenergized relay, the resistance ofresistances 51, 52

and 53 associated `with the deenergized relay, conductor 54, the tipormiddle yspring of jack 19,V plug 18, tip lead of conductors 55, meter17, the sleeve lead ,of conductors 55, to ground 56 on the sleeve ofjack 19. I'he` resistances 51, 52 and 53 are of diierent values andconsequently when current passes through any one of them, the needle ofmeter 17 will be deilected a certain amount depending onwhich resistancereceives current. Impulse lengthening circuits 57, 58 and.59 arerespectivelyprovided across the grid circuit of vacuum Atubes 44, V45and 46 in order that the negative gridjpotential may be main` tainedsufciently to cause the deenergization oi relays 47, 48`and 49, and alsoto cause the meter?, needle to maintain its deflection for a substantial length of time. i

Y Operation of the circuit of Fig. 1k

Itis assumed Vin the Vfollowing description that information is desiredregarding the magnitude,

or' the signal distortion onthe line circuit 12 which is connected toloop circuit 11. `Plugs 16 and 18 are respectively inserted into jacksk13 rand 19. Relays 2l and 22 operatein response to every change in thedirection of current in the incoming signals, for example, the relayarmatures move to their alternate or lefthand positions ,in

response to every no current or ,.openimv pulse and to their normal orright-hand posi,- tions in response to every current or closed impulse.In response to the :start or spacing impulse, which in this illustrationisa no current or open impulse, relays 21 and22 operate to theiralternate positions. Relay 22 closes a circuit extending from lgroundedbattery 25, over the armature and left contact oi relay 22,

through the winding of release magnet 26, oon-4 ductor 27, through theuppermost closed contact of jack 19 to ground 56. Magnet 26-operates andthereby releases the brush 30 which being now under the control of thefriction clutch on a driving shaft v(not shown) begins to rotate in thedirectionindicatcd by the arrow. l

If there is no distortion present in the incoming signals, every timethe armature of relay 21 moves fromone contact to the other in re'sponse to a message impulse, brush 30 will be passing over the centerline of a segment A.

l-owever, this refinementfis not necessary for the reception ofsatisfactory signals. It is com'- mon practice to allow a distortion upto about R21/2% of the dot impulse lengthand therefore it is for thispurpose that in thearrangement described herein the segments A are eachmade one-quarter of the dot impulse length and this .permits arecordation of distortion upto 121/2% on either side of the centerlineWhen the armature of relay 21 begins to move at the time brush 39 ispassing over segment A1, current from grounded battery 34 ows in acircuit extending over ring 31, brush 30, segment A1, conductor 35,through the Winding of relay 40 to ground, causing relay 40 to operate.As soon as the armature or" relay'2l reaches its opposite contact ashort circuit forbattery 34 is established and relay 40 releases. Theoperation of relay 40 momentarily connects grounded negative battery 43to the grid circuit of vacuum tube 46.` The grid oi' vacuum tube 46 isnormally at zero voltage and therefore the normal space current ofvacuum tube 46 is effective to normally maintain relay 49 in an'operatedposition. The connecting of negative .battery 43 to the grid of vacuumtube 46 momentarily plug 18, ktip lead of'conductors 55, meter 17,

sleeve lead of conductors, sleeve of jack-19 to ground '56. Resistanceelement 53 is of such valueI as toprovide on the meter va definitereading in milliammeters to indicate that there is' at the most 12 1/2%distortion.

If the distortion is in excess of 1'21/2% and lesstlian25%, brushg30will be passing over either Vthe rear portion of segment B1 or the frontportion 'of ysegment B2 at the time the armature of relay 21 starts tomove to its oppo` site contact, and a circuit will be momentarily closedwhich circuit extends from grounded battery 34,.ring 31, brush 30,segment B1 or B2, conductor 36, through relay 39 to ground. The normallyenergized relay 4S will subsequently be momentarily released in themanner described above for the release'of relay 49, to close a circuitincluding resistance element 52 and meter 17.` lResistance element 52 isof such value as to provide` on the meter a' denite; reading vindicatingthat'the distortion somewhere between 121% and 25%.

lIf the distortion isin excess of 25%,brush 30 will be passing oversegment C1 or C2 of ring 32 at the time the armature ,of relay 21ismoving from one contact to the other. Consequently a circuit will beclosed` including conductor 37 and relay 38 which circuit upon beingestablished, causes the deenergization of relay 4.7 and the closing ofthe circuit including resistance elements 51 and meter 17. Resistanceelement 51 is of suchvalue as to provide on the meter a reading,indicating distortion in excess of 25%.

The impulse lengthening circuit described above isnso chosen that if acertain `distortion value (say greater than 25%) `recurs frequentlyenough, such as once every revolution of the distributor, the meter willgive a steadyV reading.

Fig. 2 shows a distributor with rings 32 and 33 ofFig. 1 combined toform one ringSS. It is assumed that the segments of ring 33 are`designed with a View' to obtaining distortion values similar to thoseobtained by the arrangement shown in Fig. 1, namely, 0 to 121,{2%,

12/2% to 25% and in excess of 25%. The length.

of the segments of Fig. 2 will be as follows: Segments A, one dotimpulse length; segments B, one half dot impulse length; and segments C,two dot impulse length.

It is Aunderstood that by varying the number of segments, vacuum tubecircuits and resistance elements such as those designated .51, 52 and'53 in Fig. l, distortion of various values may be significant change incurrent in the impulses received over said line for selecting one ofsaid selective circuits,y and means responsive to the selected circuitsto indicate the degree of distortion present in the impulses receivedover the transmission line. i

2. In a distortionindicating lsystem for indicating the lengthening orshortening yof discrete impulses present in a transmission line, adistributor' with a common ring and a plurality of rows of segments ofdifferent fixed lengths, a path for connecting a transmission linecircuit to said common ring, a plurality of indicator circuits connectedrespectively to each of` said plurality of segments,` and a brushbridging each of said rows of segments to said commonring.

3. In .an impulse transmission system,` a plurality kof -transmissionlines, a device for indicating and measuring the distortion of` receivedsignals which manifests-itself in lengthening or shortening thedurationof signal impulses, char--` acterized in this, that a pluralityof `selective circuits respectively responsive toimpulseshavingdifferent degrees of distortion, are" provided with means for connectingthem to any one of a plurality of transmission lines and that indicatingmeans, common to the plurality of selective circuits, is provided forregistering `the degree of 'distortion in the signals received over anyone of the transmission lines.

4. In an impulse transmission system, a test circuit for indicating andmeasuring that type of distortion in received signals which manifestsitself in lengthening and shortening the duration of signal impulses,comprising a plurality of selective circuits, a rotary distributorof--the start-stop type for distributing a current impulse at every changein direction of current in the received signals, to one or more of saidselective circuits, and impulse` relaying devices for kgenerating saidcurrent impulsesfor distribution to said selective circuits, one of saiddevices being adapted to start, in response to the first impulse of eachsignal impulse combination, said rotary distributor and the other ofsaid devices being adapted to select, in response to each of thesubsequent impulses of each signal impulse combination, one or more ofsaid selecment in `said input circuit normally maintained at zeropotential, and a normally operated relay in said output circuit, andmeans responsive to the energization of the normally deenergized relayof the iirst selective circuit for momentarily applying a negativepotential to its associated control element to cause the release of itsrespective normally operated relay, means in said input circuit forprolonging the negative potential on said control element to insure therelease of the normally operated relay, and a path and a sourcecontrolled by the release of the normally operated relayfor energizingthe indicating means, each of said paths connected to each of saidnormally operated relays having an energizing eliect upon the indicatingmeans different from the effect of the other paths. l

6. In an impulse transmission system, a transmission line, a distortionindicating circuit having `terminals for connection to said line andcomprising a plurality of selecting means each respectively responsiveto signal impulses having different amounts of distortion, a distortionindicating device and means arranged to control said device exclusivelyby the selecting means responsive to 'the' largest amount of distortionwhereby said device indicates the largest amount `of ldistortion presentin a group of signal impulses.

7. In an impulse transmission system, according to vclaim 6, wherein theselecting means each includes a slow-acting device whereby thedistortion indicating'device is caused to give a steady indication ofthe magnitude of distortion when certain degrees of distortion occurrecurringly.

8. An impulse transmission system, a transmission line, va receivingcircuit and a test circuit for simultaneously receiving signals fromsaid transmission line, signal receiving means in said test circuit, `aplurality of selective circuits, responsive to every change in directionof current of the Vreceived signals, distributing means connectedintermediate said signal revceiving means and said selective circuitsfor rendering each of saidselective circuits responsive to a receivedsignal impulse having some certain degree of distortion which isdifferent, in degree of distortion, from another received signal impulsecapableof operating another of said selective circuits, and a deviceconnected to said selective circuits for indicating the degree ofdistortion.

ALLAN WEAVER.

